Delete unused loop devices before starting

Bug: N/A
Test: build with kokoro
Change-Id: Id8923a5f71be5c0139e17dda62ac0adfdebeb70b
diff --git a/build/debian/fai_config/hooks/partition.ARM64 b/build/debian/fai_config/hooks/partition.ARM64
index 31258d6..8dc663b 100755
--- a/build/debian/fai_config/hooks/partition.ARM64
+++ b/build/debian/fai_config/hooks/partition.ARM64
@@ -35,6 +35,7 @@
 ln ${device_root} ${device}p1
 ln ${device_efi} ${device}p15
 
+ls -al /dev/loop*
 losetup -a -l
 parted ${device} unit B print
 
diff --git a/build/debian/kokoro/build.sh b/build/debian/kokoro/build.sh
index cf563ef..fb2a1a3 100644
--- a/build/debian/kokoro/build.sh
+++ b/build/debian/kokoro/build.sh
@@ -3,4 +3,5 @@
 set -e
 
 cd "${KOKORO_ARTIFACTS_DIR}/git/avf/build/debian/"
+sudo losetup -D
 sudo ./build.sh